Glider pickup device



March 20, 1945 wfH. M'ccLuRE E1' AL GLTDER -PICK--UP DEVICE Filed sept. 8, 1942 2 Sheets-Sheet 1 Ilm. ...WIWIILII INVENToRs Will-'Lam H Mc'lur'e BY Bcl-h er1' C. DW

March 20, 1945.* w H, MQCLURE ET AL 2,371,635

GLIDER PICK-UP'ISEVICE Y Filed sept. 8. 1942 y 2 Sheets-Sheet 2 Patented IVI/ar. 20,1945

william H. Meciiire, United stafesNavy, and Robert B.`!Cotton, DrexelgHill, Pa.

Application september s, 1942 srialNo. 457,685` r "f 12 claims. (cran-c3) (Granted underfthe' set .of VMarch 3,' 1883, f as i amended aprirsi), 192s; 37o 0.o. 757

Another object is to be able ,to do thisfwith steady and not excessive acceleration of-jthe glider, using a' minimum of apparatus which `has to be carried aloft by either plane or glider` other than the necessary tow line.` A further object is to pick up a glider from the ground by a plane in night with kthe least expenditure .of energy and without shock. j

A still further object is` to provideapparatus rwhereby the force 'transmitted from an airplane in flight to a glider on the ground may be maintained at a predetermined constant, `until the around the sheave atC back the glider 9 is directly proportional't'o tension in speed of the glider reaches that of the plane, l

whereupon the apparatus is released and the glider towed thereafter directly by a separate towline. l n

A still further object ,is to reduce the force transmitted from an airplane to the glider which it is to pickup to one half of that necessary to give the glider a predetermined acceleration, by temporarily supplying the other half thereof by means on the ground until` the speed of the gliderreaches that of the plane.

A still further object is to provide safety feal tures for the apparatus abovereferred to, to avoid excessive strain at either theplane or the glider attachments. u

Further objects `will assert themselves as `the description of this invention proceeds,-having reference to the accompanying drawings, in which:

Fig. 1 illustrates one form `of the general layout i of thelines preparatory to launching.` i

Fig. 2 shows diagrammatically ona larger scale some of the apparatus used in connection with the above layout, and the `plane an instant after its Fig. 1 position. l i

Fig. 3 is aiperspectivelview ofthepoles and arrangement of the cables with -respect thereto preparatory to being picked up by the hook onthe airplane, f

Figs. 4 and 5 are enlarged viewsv of the release mechanism shown'at G'inFig. 1,prior to and immediately after'release, respectively,,and

' Figs.` 6l to 9 are curves showing the `character- SUCS Qf,Ollidfesgrr0f` the apparatus operating inV accordance withrone given setof conditions as an exampl'e-to illustrate `the operation of `the device-` N t V. l i Referring more particularly to the drawings, the hook I attached to airplane 2 engages cable 4loop 3 at a 20 ft. span shown at A; As the cable is engaged, the standards 4 are released "at B and are pulled tothe ground bytheshock cords 5. The load is transmitted through` cable `Y to and around the sheaves of a hydraulic-plunger '6 to theanchor dashpot shown at D. The load in the cable Y increases 'the'pressure inthe dashpot which opens aspringloaded" valve at E. This opens arr ac- `cumulatorfflv loaded with highlpressure air and oil to the hydraulic cylinder 18.` Arelief valve at F limits the peak pressure. The acceleration "of cable Y, which is directly proportional `to the ,accumulator pressure. `The glider accelerates at" a constant acceleration. From the start until `the time that the glider reaches one-half the speed the accumulator. At thel time the glider reaches half the speed of theairplane, the hydraulic plunger ceases to act as a shock unit and becomes a catapult. At this `point H, the velocity of the plunger becomes zero and Vchanges.direction as shown in Fig. 1. .While cable Yis accelerating the glider tothe speed of the airplane,` cablef X is fed Vout from a drum in the glider. The velocity of came X in rennen to thegnder .is-snown. in Fig. 9. When this velocity reaches a' very 4low value, a governor which is synchronized with the drum causes a.

. cable X with relationto theg'lider. A tension is therefore created in cable X, which pulls the release at G, which releasescable Y, the initial tow cable. The hook on'the airplane contains a spring the pressure in the anchor dashpot at D is rein friction. All the rest of the energy transmitted duced, which closes the valve at E, thus bringing the plunger 6 to a stop, The 'plunger the same position as in starting position.

The chief advantages of this gliderxpickLup method areas followsl i 1.,The only energy absorbed isthef'energy lost from the airplane is useful energy trip to lock the drum, `whichstops is now at for launching many gliders.

2. Nearly constant acceleration of the glider is obtained, as shown in Fig. '7.

glider, reference Fig. 1.

y 4. Very little equipment is carried in the airplane or glider, thus the equipment can be used 5. The 'span and runout are small. enough to K adapt this methodvto the deck of a ship.

The characteristic curves in Figs. 6 to 9 are,V based on the assumption that the hydraulic plunger mechanism has a mechanical advantage of approximately to l, there being ten tpulleys or sheaves at each end of the plunger mechanism around which the cable Y is successively .passed before it goes to the dash pot D. The airplane speed is assumed to be 100 miles/hr. "The pressure in the hydraulic cylinder 4is so adjusted 'that the force pulling the glider will 'be equal to that necessary to give it an acceleration of 1.5 times V .einemgravity. Fora 110,000 ib. giiderytms force would be (Tlf0,000 i.5`9 or `155000 lbs. causing la tension 1iny :cable Y fof 7500 lbs. With l'this .ap-

plied force, the time taken for the glider'to'reach and the distance covered by the glider rin; this time would fbe f 'To supply the Acable rto the sheave yat 'they glider fat the rate of .100 miles/hr. at the start,

thehydraulicplunger has -to assumera speed tofmiles'lhr., the velocity .of this plunger will -re duce until rat .the pointH where the glider has attained a speed 'of half of `thatcf the airplane, the plunger speedwill be zero and will then reverse 'in direction and gradually increase.

n If we assume .the airplane lto Weigh 20,000 lbs. thel speed lof the' airplane .and glider vat the -time when the glider reached' Ythe speed of .the 4airplane would be p Vn=fapprox. B2 miles/1hr.

iff*v no p'ower'were add-ed by 'the engines in the meantime, 'otherthan that su'ic'ient 'to overcome resistance; sinceA the .loss fin kinetic `energy of theairplane is equal tothe gain .in kinetic `energy of th'eg'li'der:

` '/zlVfT/blmI/J 20200600 VQ? ioogov.

le' Nill V4 3 @r approx.- 2182 miles/hr.

a'tension of 7500 lbs. in cable Y is assumed to be 5000 lbs. p. s. i. The capacity should be about 40 cu. ft. in this case in order to maintain a substantially constant pressure. The valve E is set to open'when the tension in the cable exceeds 2000 lbs. The relief valve F is set to open at 5500 lbs p. s. i. The fluid in the dashpot control lline vmay -be under air pressure of 100 lbs. p. s. i. at il). The tank at Il for catching the excess hydraulic iiuid may be open 4to atmosphere.

Other values and dimensions may be used on this apparatus. For example, if the pressure in Vthe accumulator be reduced to 2500 lbs. p. s. i., the following changes would have to be taken into account: f

l. The .glider runout would be increased to Icai'fion's may be madertherein without departing l2. `The airplane runout would increase to from the basic essentials illustrated.

This invention may be used by er fior the Government of thel'United States ffcr gcvernrnenta1 purposes Without itl-1e Ipayment to us fof rany royalty thereon-for'thereiior. f

.1. A method df A pickin-g -=p :gliders `in tow by an aircraftiin flight-including the transmission of Ia constant 'force iof :a predetermined magnitude from iithe :aircraft to the :glider until 'the flatter attains :the speed 'of 'itheifor-m'er', followed by esi tablishing a towing connection at such distance as exists between the .aircraft andthe glider at that atime.

2.111 ra fglid'erlaunching and 'ltow-ing system wherein :an faircrafft'fin flight picks .up a glider from ra iposition tof rest Ion4 .the ground, a-rcable, a lshea-ve hodkedrunder the nose lof Ithe glider, means for supplying a substamtia-llyconstant1tension at one Iend of fthe cable at la idistance 4in front of the .,glider, theic'a-ble being lpassed around saidsheaveandfthe otherlendpf itibe'in'g stretched forward and hung up to facilitate its .being @picked up from the .mean-s 4.on ith'e aircraft :for -picking \up;said ptherfendoitheicable, aurelease'mechanism inthe cable inear'fsaid other end, :a `.reel in the nose of the glider, a tow line connected to` said mechanism .and to .said reel, Arneans responsive to .fa predetermined 'tension 'in isa'idy ftowline to ioperatezsaid imechanism to :release :said

.3. :In a glider vlaunching sand .towing :system wherein an aircraft in night picks rip a :glider from a ,position -of .rest fon fthe fg-round, a cable, a y.sheave luoekedmridier vthe nose lof fthe glider.,- means for .supplying a substantiallyconstantttension at one end of the cable at a distance "infront .of .the slider., `the cableibeing l#passed around said sheave and theretliersendiofit.beingstretchedA forward and hung up yto.facilitate -ts beingpked upV from l:the air, means onthe aircraft for pickwherein an aircraft in fiight picks upa glider from a `position of rest on the ground, a cable, a sheave hooked under the'nose ofthe glider,

means located at a distance in front of the glider i for supplying a substantially constant tension to the cable, one end of the cablel being passed around said sheave and then to thev tension supplying means, and the other end of it being.

stretched forward and hung up to facilitate its being picked upfrom the air, means on the aircraft for picking up said other end of the cable, a release mechanism in the cable near` said other end, a reel in the nose of the glider, a vtow line connected to said mechanism and to said reel, means responsive to a predetermined tension in said towline to operate said mechanism to release said cable, means normally allowing the reel to pay out the towline as the distance be-` i tween plane and "glider increases but stopping said reel when the rate of increase of Lsaid distance is reduced below a predetermined minimum, thus increasing the tension in the towline to release the cable and cause it and the sheave to fall to the ground. i

5. The combination defined in claim 4 in which constant tension supplying means consists of a constant tension supplying means consists of a `hydraulic catapult device having a suitable mechanical advantage, meansior maintaining a substantially constant hydraulic pressure therein, including a pressure accumulator or reservoir for thehydraulic fluid connectedtothe catapult cylinder, said connection having a control valve which is normally closed, a dash pot connected by a line to said valve which opens in response to pressure in said dash pot line, the end of the cable at the tension supplying means being connected tosaid dashpot to transmit a force thereto,

and thereby produce said pressure when the cable ispicked up by the aircraft. l A 1K0. The combination defined in claim 4` in which constant tension supplying means consists of a hydraulic catapult device having a suitable Imechanical advantagaand means for maintain-` ing a substantially constant hydraulic pressure therein, including a pressure accumulator or reservoir for the hydraulic uid connected tothe catapult cylinder, said connection having a control valve, which is normally closed, a dash pot I connected by a line to said valve which opens in response to pressure in said dashpot line, the end i of the cable at the tension supplying meansv being connected to said dash-pot to transmit a force thereto, and thereby produce said pressure V when the cable is picked up by the aircraft, said hydraulic catapult device having a suitable mechanical advantage, and means for maintaining a substantially constant hydraulic pressure therein. i l

6. The combination defined in claim 4 in `which the pick-up end of the cable is looped, said loop being stretched over hooks mounted at the top of spaced poles to facilitate the pick-up.`

7. The combination defined in claim 4 in which the pick-up end'of the cable is looped, the loop being hung across the tops of a pair of spaced poles rto facilitate the pick-up and means for throwing the poles to the ground when the loop A is picked up. l

e. The combination denned in claire 4 in which constant tension supplying means consists of a i hydraulic catapult device having a suitable mechanical advantage, and means formaintaining a substantially constant hydraulic pressure therein, including a pressure accumulator or reservoir for the hydraulic fiuid connected to the catapult cylinder.

9. The combination defined in daim 4 in which rst 4mentioned connection also having a pressure relief valve connected theretb with adjusting means for controlling the maximum pressure permitted in the catapult cylinder.

i l1. Apparatus for picking up a glider in tcwby an aircraft in ight, includinga cable to be picked up by one end by the aircraft, a sheave on the nose of the glider, a source of constant tension on the ground ahead of the glider in the direction of flight, the other end of said cable being passed around said sheave and then to said source, and means for establishing a towing connection after the cable is picked up and the speed of the glider approaches that of the airplane.

r 12. Apparatus for picking up a glider in tow by an aircraft in flight, including a sheave on the nose of the glider, a source of `constant tension on the `ground ahead of the glider in the direction of flight, a cable to be picked up by one l end by the aircraft, the other end being passed` f around said sheave to said source, means for establishing a towing connection after the cable `is picked'up and the speed of the glider aplproaches that of the airplane, and means for detaching` the cable from the aircraft and the l sheave on the nose of the glider.

WILLIAM H. MCCLURE. ROBERT B. COTTON. 

